Pintle valves are well known for use in controlling flow of fluids, and especially gases. For example, the recirculation of a portion of the exhaust stream of an internal combustion engine into the intake manifold thereof is typically accomplished via a solenoid-actuated pintle valve. Such applications can expose a valve's internal surfaces and moving parts to fouling materials. A pintle-type exhaust gas recirculation (EGR) valve is exposed to moisture-laden corrosive materials which can seep into the clearance between the valve pintle shaft and the pintle bushing. Such materials can deposit as undesirable coking on the shaft, but can also pass through the bushing and enter the solenoid actuator where they can cause impairment or failure of the actuator.
The moisture intrusion phenomenon is facilitated by the fact that a journal shaft bearing (bushing) is employed that inherently incorporates radial clearances to minimize hysteresis. Such clearances can allow corrosive gases to leak past the bushing in small amounts, which gases are known to condense within the solenoid actuator, causing corrosion of the coils and eventually electrical short-circuiting.
In some prior art EGR valves, a space is provided between the valve body and the actuator, which space may be vented to permit escape of such gases leaking along the bushing, preventing the gases from being forced into the actuator solenoid. However, such vents may also permit ingress of external contaminants, especially water and road contaminants when a valve is subjected to intense spray or temporary immersion. These contaminants may then be drawn into the actuator and also cause mechanical and/or electrical failure of the device.
What is needed in the art is a means for keeping corrosive gases being regulated by a pintle-type valve from reaching entry points on an associated solenoid actuator.
It is a principal object of the present invention to increase the reliability of an exhaust gas recirculation valve by preventing contaminating materials from passing through the valve bushing and entering the solenoid actuator.